Nepal's former Maoist guerrillas were poised to return to power today after two years, as Parliament readied to elect the restive republic's fourth Prime Minister in three years.

Nepal's former Maoist guerrillas were poised to return to power on Sunday after two years, as Parliament readied to elect the restive republic's fourth Prime Minister in three years.

Maoist deputy chief Baburam Bhattarai, a board exam topper and doctorate degree holder from New Delhi's Jawaharlal Nehru University (JNU), was poised to become Nepal's 35th Prime Minister, with his party clinching a last minute deal with a bloc of five ethnic parties, whose support holds the key to Sunday's election.

Even before the election started, Bhattarai enjoyed an edge over his rival, Ramchandra Poudel of the Nepali Congress party, as the Maoists are the largest party in parliament with 237 seats in the 601 seat Parliament, while the Nepali Congress has 114 lawmakers.

Due to the death of some MPs and some being stripped of parliamentary membership, there are currently 594 MPs and the winner would need 298 votes to claim majority support.

The Madhesi Morcha, five parties from the Terai plains who have 71 MPs, on Sunday said they would support Bhattarai, thereby clinching his victory except for a major upset.

A fringe left party, Jana Morcha with five lawmakers, also said it would support Bhattarai.

Poudel, a former deputy Prime Minister who had been the Nepali Congress' candidate in the earlier 17 rounds of vote, had received a shot in the arm on Saturday night with the third largest party, the communists, announcing they would support him.

However, despite the 108 communist MPs behind him, Poudel still faces an uphill task to win the election.

Unlike the last polls that spanned over seven months and saw 17 rounds of voting in parliament, Sunday's election will be decisive due to a change in poll regulations that prevents lawmakers from absenting themselves or staying neutral.

The Maoists, who after fighting a 10-year war signed a peace accord in 2006 and won the election in 2008, are now offering to disband their guerrilla army within 45 days of forming the new government under their leadership.

The existence of the People's Liberation Army (PLA), with its nearly 20,000 fighters even five years after the insurgency ended, is regarded as the main obstacle to the peace process and led to the fall of the first Maoist government of Nepal in 2009.

Bhattarai is regarded as the moderate face of the Maoists, whose chief Pushpa Kamal Dahal Prachanda failed to return to power after backtracking on his promise to demobilise the PLA, return the properties captured by the rebels during the civil war, and end the culture of impunity that saw both the state and Maoists carry out torture and extrajudicial killings.

The new premier will face an acid test soon.

Three days later parliament needs to enforce a new constitution or face dissolution.

Nepal's major parties, warring for power, failed to write the new constitution despite the deadline being extended twice. Now the caretaker government of outgoing minister Jhala Nath Khanal is seeking to extend the Aug 31 deadline by three more months.

If the extension comes through, the new premier will have to win the support of all the major parties and ready the first draft of the constitution as well as discharge the PLA.